UPDATE 1-Finnish nuclear consortium Fennovoima dismisses CEO

* Board lacked confidence in Saarenpaa for "new phase"

* Board chairman left in Sept

(Adds spokeswoman comment, background)

HELSINKI, Oct 1 (Reuters) - Finnish nuclear consortium Fennovoima dismissed its chief executive, saying it needed a different leader for its new phase, as it moves ahead with plans for a nuclear plant in Pyhajoki, northern Finland.

Fennovoima's board decided Chief Executive Tapio Saarenpaa should be "relieved of his duties", the company said.

"The CEO operates with the confidence of the board, and when the day comes when there is not enough of that, this is what happens," Fennovoima spokeswoman Maira Kettunen said, declining to elaborate.

The move comes as Fennovoima prepares to choose next year between Areva and Toshiba to supply the Pyhajoki reactor.

It also comes on the heels of Fennovoima chairman Juha Rantanen's announcement last month that he would leave, handing over the post to Pekka Ottavainen. Rantanen had also cited a "new phase" of planning for Pyhajoki.

The plant is due to provide cheap energy to its shareholders including stainless steel maker Outokumpu , retailer Kesko and the local subsidiaries of Swedish metals firm Boliden .

Its biggest single shareholder is German utility E.ON's

Finnish subsidiary with a 34 percent stake.

Fennovoima said it would look for a new CEO, and that Juha Nurmi, a project manager at Fennovoima, would take on leadership temporarily.

(Reporting by Terhi Kinnunen; Editing by Helen Massy-Beresford)

((terhi.kinnunen@thomsonreuters.com)(+358 9 680 50 243)(Reuters Messaging: terhi.kinnunen.thomsonreuters.com@reuters.net))